The present invention, which is the subject matter of U.S. Disclosure Document No. 058305 filed Feb. 28, 1977, relates to return springs for autoloading firearms, and it relates more particularly to multi-spring assemblies for slide-type automatic pistols in which a breech-member compresses a coil spring as it moves out of breech-closing or battery position and is returned to battery by the spring.
In spring-reliant apparatus of various kinds, in which there is a limited amount of space for housing a coil spring, it is frequently difficult to design a spring or spring system which is capable of releasing its stored energy at the desired rate throughout the required distance of travel. This problem is encountered in the design, or redesign, of small automatic handguns where it is desired to make the gun as small as possible, yet capable of firing ammunition of the suitable caliber for self-defense purposes. Typical of such weapons are the well-known Colt .45 and 1911 Government automatic, both of which have been used by the United States armed services for many years. In this type of pistol, the breech-bolt forms part of a slide, that reciprocates on the frame and totally surrounds the barrel when in battery position, the slide being driven rearward by the recoil of the gun when fired and returned to battery by a recoil spring. Since the slide meets with some resistance during its forward movement into battery, including for example, overcoming inertia and friction between it and the frame, as well as in stripping a fresh cartridge from the magazine and in this case in locking the slide to the barrel, the return spring must store considerable energy in order to ensure reliable action.
The difficulty with most automatic pistols of this type is that for personal defense purposes the barrel and slide are too long, making them too bulky to carry concealed on the person. To my knowledge no way has been found heretofore to reduce the length of the barrel and slide without adversely affecting the performance and/or safety of the gun, due to the space limitations for the recoil spring which such shortening imposes. In fact, where the length of the barrel and slide are reduced below that of Colt's "Combat Commander", it has been found by discriminating gun experts to be impossible to design a return spring that functions properly.
Although a number of different techniques have been used in attempts to overcome the spring problem created by the necessity of shortening the slide as well as the barrel in such guns, none of the methods employed heretofore offers anything approaching a satisfactory solution. Prior efforts using telescoping recoil springs to shorten the slide and barrel of the Colt .45, for example, have resulted in very little spring pressure when the slide is forward in battery, so that any gain in the reduced size of the gun has been dearly paid for in reliability. In many instances, the free length of the recoil spring barely exceeds its compressed length at battery, with the resultant spring load being so poor that the slide is not held firmly in breech-closing position during normal handling of the pistol, thereby severely reducing the quality and performance of the spring action.
In addition to the single recoil-spring typical of the slide-type automatics, are multi-spring arrangements shown for example in U.S. Patents to Browning, No. 580,924, Zimmerman, No. 3,731,590 and Border et al, No. 4,040,332. Browning U.S. Pat. No. 580,924 discloses the use of a buffer spring in conjunction with the typical recoil spring employed in one of the early Browning automatic pistols which preceeded production of the Government Model 1911 designed by John M. Browning. In the Zimmerman patent a take-up spring is used inside a conventional recoil spring for an autoloading pistol. However, in this system the take-up spring is arranged so that it works in opposition to the recoil spring. In the Border et al U.S. Pat. No. 4,040,332, a variable spring rate is produced by employing two coil springs of different rates end-to-end with a floating piston between them.
In addition, the Swiss semi-automatic sporting rifle known as the SIG-AMT manufactured by Swiss Industrial Company of Neuhausen Rine Falls, Switzerland, employs a multi-spring recoil system which is similar to that of my invention, but differs in important respects, with the result that it is incapable of being employed in situations where space is severely limited. Thus, in the SIG rifle the recoil spring assembly consists of telescoping springs which are connected in tandem by an elongate coupling sleeve. However, the SIG spring assembly is not suited for use in slide-type automatic pistols due to the large coil diameter of the outer spring necessitated by the complexity of the system and its many telescoping parts. Furthermore, the SIG arrangement does not allow compression of the spring assembly beyond the space taken up by the longest of its component parts, including guide and support units, so that the arrangement does not provide a solution to problems arising from severely restricted space.
Attention is also directed to the buffer spring arrangements shown in a United States Government book published in 1955 entitled The Machine Gun, Design Analysis of Automatic Firing Mechanisms and Related Components compiled by George M. Chinn (Vol. IV, parts X and XI). Example A of FIG. 15-5 on page 487 of this publication shows a recoil spring assembly comprising a buffer spring and barrel return spring acting in series. Here again space for the springs is not a controlling factor, and the coupling sleeve connecting the two springs merely serves to limit the amount of deflection of the barrel return spring and to properly position the buffer spring.
Other instances in which multiple-coil springs are used for absorbing the recoil of a firearm and for returning the action to battery position are the Detonics automatic pistols made by Detonics .45 Associates of Seattle, Washington, and the custom Colt .45 Associates of Seattle, Washington, and the custom Colt .45 shortening jobs done by Pachmayr Gun Works of Los Angeles, California, and by Behlert Custom Guns, Inc. of Union, New Jersey. In each of these guns, a pair of recoil springs are used, one within the other (and with right and left hand helix to prevent entanglement with each other). Each spring engages both the slide and frame, so that they act in parallel. This spring configuration can be found in FIG. 28, page 45, of a book entitled Spring Design and Application, which is edited by Nicholas P. Chironis and was published in 1961 by the McGraw-Hill Book Company, Inc. of New York.